This invention relates to a filter apparatus for filtering a liquid such as cutting oil or abrasive oil by removing solid foreign matter such as cutting chips and abrasive grains from the liquid.
Factories exist in which a variety of machine tools are installed for machining metal materials. These machine tools make use of cutting and abrasive oils employed in a circulating manner. The system through which the oil is circulated is provided with a filtration apparatus for filtering the oil by separating the cutting chips or abrasive grains from the cutting or abrasive oil containing this foreign matter. One such filtration apparatus known in the art is a mesh filter apparatus.
A mesh filter apparatus is provided with a filter which allows only a liquid to pass therethrough following capture of the foreign matter contained in the liquid, and a scraper adapted to prevent clogging of the filter by scraping off the foreign matter that the filter has captured.
When a cloth filter or wire mesh is used as the filter employed in the aforementioned mesh filter apparatus, the cloth or wire mesh captures the cutting chips or abrasive grains efficiently but these contaminants tend to become caught in the woven or knitted portions of the cloth or wire mesh. Once this occurs, it is very difficult to remove the cutting chips or abrasive grains from the filter. Even though the surface of the filter is scraped by the scraper, the clinging foreign matter cannot be scraped off with ease and the filter cannot be reclaimed in an effective manner.
If a brush is used as the scraper in the above-described mesh filter apparatus, the foreign matter becomes trapped in the brush and grows into a large deposit that detracts from the scraping action of the brush in a short period of time.
In an effort to eliminate the aforementioned drawbacks, the applicant has already developed a mesh filter apparatus in which the filter member is a smooth-surfaced thin sheet having a multiplicity of through-holes, an example of the filter member being a punched metal sheet. Scrapers each comprising a resilient blade are brought into sliding contact with the front and back surfaces of the filter made of the thin sheet. Applications claiming this mesh filter apparatus have been filed in Japan, the U.S.A. and other countries (see the specifications of Japanese Patent Publication No. 60-014603 and U.S. Pat. No. 4,437,991).
Since the front and back surfaces of the sheet are smooth in the disclosed mesh filter apparatus, little of the trapped foreign matter clings to the sheet. Moreover, the scrapers are blade-shaped and therefore these also attract little of the foreign matter. Thus the apparatus is advantageous in that the foreign matter can be scraped off in smooth fashion.
However, a problem is encountered in that the structure of the above-described mesh filter apparatus is such that the mesh filter is disposed across a wide area near the outlet of a tank accommodating the cutting or abrasive oil, and the scrapers are in sliding contact with the front and back surfaces of the mesh filter. In other words, the mesh filter is fixed and the scrapers travel on both sides of the filter. As a result, not only is a large amount of space needed to install the mesh filter apparatus, but the scraper drive mechanism for moving the scrapers is of some complexity.